Field Testing and Analysis of CRC Deck Girder Bridges

This paper presents findings of field tests and analysis of two conventionally reinforced concrete (CRC) deck girder bridges designed in the 1950s. The bridges are in-service and exhibit diagonal cracks. Stirrup strains in the bridge girders at high shear regions were used to estimate distribution factors for shear. Impact factors based on the field tests are reported. Comparison of field measured responses with AASHTO factors was performed. Three-dimensional elastic finite-element analysis was employed to model the tested bridges and determine distribution factors specifically for shear. Eight-node shell elements were used to model the decks, diaphragms, bent caps, and girders. Beam elements were used to model columns under the bent caps. The analytically predicted distribution factors were compared with the field test data. Finally, the bridge finite-element models were employed to compare load distribution factors for shear computed using procedures in the AASHTO LRFD and Standard Specifications.     

Performance Assessment of a Precast-Concrete, Buried, Small Arch Bridge

Experimental field load-test and finite-element analysis were carried out for the performance assessment of a precast-concrete, modular, three-sided, low-profile, buried, arch bridge system. Finite-element analysis incorporated soil modeling and soil–structure interaction at service and limit load levels. The analytical study simulates step-by-step incremental phases of construction and service loads. The finite-element model was calibrated based on the experimental field assessment, to provide a better correlation between the analytically predicted behavior and the actual response of the structure. The study validates the incorporation of various soil models and soil–structure interaction characteristics, to allow a more cost-effective bridge design.     

Dynamic Analysis of a Composite Cable-Stayed Bridge: Escaleritas Viaduct

This work describes some of the most important results of the experimental and numerical analyses of Escaleritas Viaduct, Spain. Before the inauguration of this composite cable-stayed bridge in 2006, the bridge authority required a dynamic load test identifying, for instance, the natural vibration modes, the dynamic magnification factor, and the maximum vertical acceleration. The dynamic test was accompanied by numerical simulation performed in two different three-dimensional finite-element models, one of them composed of 145,000 shell elements. The correlation of test and analysis data is good and allows several interesting general conclusions to be drawn. It is shown that Escaleritas Viaduct complies with the requirements on the dynamic structural behavior defined in the standards.     

Finite-Element Analysis and Vibration Testing of a Two-Span Masonry Arch Bridge

This paper presents the analytical modeling, modal testing, and finite-element model updating for a two-span masonry arch bridge. An Ottoman masonry arch bridge built in the 19th century and located at Camlihemsin, Rize, Turkey is selected as an example. Analytical modal analysis is performed on the developed 3D finite-element model of the bridge to obtain dynamic characteristics. The ambient vibration tests are conducted under natural excitation such as human walking. The operational modal analysis is carried out using peak picking method in the frequency domain and stochastic subspace identification method in the time domain, and dynamic characteristics (natural frequencies, mode shapes, and damping ratios) are determined experimentally. Finite-element model of the bridge is updated to minimize the differences between analytically and experimentally estimated dynamic characteristics by changing boundary conditions. At the end of the study, maximum differences in the natural frequencies are reduced on average from 18 to 7% and a good agreement is found between analytical and experimental dynamic characteristics after finite-element model updating.     

Seasonal Frost Effects on the Soil–Foundation–Structure Interaction System

This paper presents the results of more than one year’s monitoring efforts and analysis of the effects of environmental variables on the dynamic properties of a selected bridge in Anchorage, Alaska. A seismic monitoring system was installed on the bridge to study these effects. The dynamic properties of the bridge have been identified from the recorded time histories which include ambient noises, traffic-induced vibrations, and small-magnitude earthquakes. Hourly air temperature data from nearby meteorological station during the period of study were collected to estimate the frozen soil depth for modeling purpose. A finite-element model and multiple-input autoregressive model were applied to study the effects of environmental variables on the dynamic properties. The results show that the environmental variables can significantly affect the dynamic properties by modifying the stiffness of the bridge system and the seasonal frost is found to have the dominating effects over air temperature on the bridge dynamic properties in cold regions. The results show that the models explain well the variation of dynamic properties with environmental variables.     

AASHTO-LRFD Live Load Distribution for Beam-and-Slab Bridges: Limitations and Applicability

This paper presents a comparison between the live load distribution factors of simple span slab-on-girders concrete bridges based on the current AASHTO-LRFD and finite-element analysis. In this comparison, the range of applicability limits specified by the current AASHTO-LRFD is fully covered and investigated in terms of span length, slab thickness, girder spacing and longitudinal stiffness. All the AASHTO-PCI concrete girders (Types I–VI) are considered to cover the complete range of longitudinal stiffness specified in the AASHTO-LRFD. Several finite-elements linear elastic models were investigated to obtain the most accurate method to represent the bridge superstructure. The bridge deck was modeled as four-node quadrilateral shell elements, whereas the girders were modeled using two-node space frame elements. The live load used in the analysis is the vehicular load plus the standard lane load as specified by AASHTO-LRFD. The live load is positioned at the longitudinal location that produced the extreme effect, and then it is moved transversely across the bridge width in order to investigate all possibilities of one-lane, two-lane and three-lane design loads. A total of 886 bridge superstructure models were built and analyzed using the computer program SAP2000 to perform this comparison. The results of this study are presented in terms of figures to be practically useful to bridge engineers. This study showed that the AASHTO-LRFD may significantly overestimate the live load distribution factors compared to the finite-element analysis.     

Performance of a Tied-Arch Reinforced Concrete Railway Bridge: Rating, Safety Assessment, and Bond Length Evaluation

This study presents investigations regarding visual inspection, dynamic testing, and finite-element modeling of an approximately 80-year old reinforced concrete tied-arch railway bridge that is still in service in Turkey. Investigations were conducted as part of a systematic periodic inspection along Ankara-Zonguldak railway line. The bridge is subject to heavy freight trains with increasing axle loads. Field tests such as material tests and dynamic tests were used to calibrate the finite-element model of the bridge. Detailed information regarding testing and model updating procedure is given. Based on test results, computer model was refined. The calibrated model of the bridge structure was then used for structural assessment and evaluation. Despite sufficient overall safety, local details were found to be problematic. Due to insufficient bond length in hanger-to-arch connection, a strengthening scheme using steel channel sections was proposed.     

Integral Abutment Bridge Behavior: Parametric Analysis of a Massachusetts Bridge

Integral abutment bridges are often a preferred bridge type for moderate spans throughout the United States. However, design methods and construction details vary from state to state. Variations between states are noted in the methods employed to accommodate deformations in the piles. The significance of these differences was evaluated through a finite-element study. The effects of backfill properties and soil restraint on piles were evaluated with regard to bridge distortions and maximum moment realized in the piles. Results show that bridge expansion is predominantly affected by backfill conditions, whereas contraction is influenced by pile restraint conditions. Pile moments are minimized when denser backfill and lower pile restraint are provided. The influence of abutment soil-structure spring modeling assumptions is addressed. Models were calibrated to the reference bridge at Orange-Wendell, Mass, which has been instrumented and data collected for 4 years.     

Simplified Braiding through Integration Points Model for Triaxially Braided Composites

A simplified methodology has been developed for modeling two-dimensional triaxially braided composite plates impacted by a soft projectile using an explicit nonlinear finite-element analysis code LS-DYNA. The fiber preform architecture is modeled using shell elements by incorporating the fiber preform architecture at the level of integration points. The soft projectile was modeled by an equation of state. An arbitrary Lagrangian–Eulerian formulation is used to resolve numerical problems caused by large deformation of the projectile. The computed results indicate that this numerical model is able to simulate a triaxially braided composite undergoing a ballistic impact effectively and accurately, including the deformation and failure with a reasonable level of computational efficiency.     

Dynamic Testing for Structural Identification of a Bridge

Structural identification via modal analysis in structural mechanics is gaining popularity in recent years, despite conceptual difficulties connected with its use. This paper is devoted to illustrating the advantages and also the indeterminacy characterizing structural identification problems for bridge structures, even in rather simple instances. In particular, an identification procedure based on modal analysis and finite-element model updating is presented for the characterization of a concrete bridge whose constructive typology is quite diffuse in the area of Friuli Venezia Giulia, Italy. Experience has suggested (so as to restrict the indeterminacy frequently affecting identification issues) resorting to all the a priori information on the system and mindfully selecting the parameters to be identified. The analysis pointed out some particularities in the modeling of bridge typology under study, otherwise not a priori detectable from an analytical point of view.     

Finite-Element Analysis of Tapered Steel and Fiber-Reinforced Plastic Bridge Camera Poles

This paper presents experimental and finite element investigations of the load-deformation behavior of tapered steel and fiber-reinforced plastic (FRP) bridge camera poles subjected to cantilever bending type loading. Three full-scale experimental tests are conducted on one tapered octagonal steel cross section and two FRP circular cross-section poles to identify their load deformation characteristics. Three-dimensional isoparametric finite-element models of the poles are developed by considering the nonlinear coupling behavior between material, contact, and geometric effects. The elastoplastic solid elements with eight nodes are employed for the effective three-dimensional finite-element modeling and analysis. A surface-to-surface contact algorithm is used to simulate the interaction between contact surfaces. An energy-based convergence criterion is adopted to obtain the converged coupled nonlinear solutions. The obtained load-deformation results from finite-element analyses are compared with those of the experiments. The behavior of the finite-element models is examined by observing the effects of individual geometric variables on the load-deformation characteristics of the poles.     

Development of Finite-Element Modeling Approach for Lateral Load Analysis of Dry-Glazed Curtain Walls

This paper presents a finite-element modeling option to provide an analytical approach for a seismic analysis of dry-glazed curtain-wall systems. In this modeling approach, Ansys finite-element software was used to model the glass panel, aluminum glazing frame, perimeter rubber gaskets, rubber setting and side blocks, glass-to-frame clearances, and glass-to-frame contact once the clearance was overcome by in-plane drift. The results of the finite-element modeling of the curtain-wall system were compared with full-scale laboratory test results. The effect of some of the parameters such as gasket friction and aspect ratio were evaluated. The study showed that finite-element modeling is a viable approach for analytical evaluation of curtain walls. The modeling can function to predict the drift associated with glass-panel cracking. Further refinement of the modeling approach developed can increase the accuracy of the prediction.     

Live-Load Distribution Factors in Prestressed Concrete Girder Bridges

This paper presents an evaluation of flexural live-load distribution factors for a series of three-span prestressed concrete girder bridges. The response of one bridge, measured during a static live-load test, was used to evaluate the reliability of a finite-element model scheme. Twenty-four variations of this model were then used to evaluate the procedures for computing flexural live-load distribution factors that are embodied in three bridge design codes. The finite-element models were also used to investigate the effects that lifts, intermediate diaphragms, end diaphragms, continuity, skew angle, and load type have on distribution factors. For geometries similar to those considered in the development of the American Association of State Highway and Transportation Officials Load and Resistance Factor Design Specifications, the distribution factors computed with the finite-element models were within 6% of the code values. However, for the geometry of the bridge that was tested, the discrepancy was 28%. Lifts, end diaphragms, skew angle, and load type significantly decreased the distribution factors, while continuity and intermediate diaphragms had the least effect. If the bridge had been designed using the distribution factors calculated with the finite-element model rather than the code values, the required concrete release strength could have been reduced by 6.9 MPa (1,000 psi) or the live load could have been increased by 39%.     

Effect of Construction Loads and Vibrations on New Concrete Bridge Decks

This paper presents an investigation on the effects of construction loads and vibrations on typical newly poured reinforced concrete bridge decks. The main objective of this paper was to perform dynamic finite-element analyses of concrete bridge decks under construction loads and vibrations. Two types of bridges were modeled by effectively simulating the loads encountered during construction. Separate analyses were performed to simulate one truck as well as two side-by-side trucks. Additional analyses were performed to simulate the loads during construction and pouring sequence. The loads imposed by concrete mixer trucks, including the full concrete load and the load imposed by a trailer unit carrying the pump, were taken into consideration during the modeling of the bridges. The results obtained consisted of vibration modes and frequencies for each structure in addition to top and bottom stresses in each principal direction. A separate analysis was performed that took into account the sequence of pour to determine the effect of moving loads from adjacent traffic and construction loads on fresh concrete. The time history and dynamic analysis indicated that the sequence of pour has a significant effect on the deformation of the concrete at early ages. As a result, the first three mode shapes obtained by the finite-element analysis will be used to optimize sensor locations for future dynamic field testing.     

Improving the Response of Soil-Metal Structures during Construction

For economic reasons, manufacturers of soil-metal bridges have strived to build these structures under the shallowest possible depth of soil cover, below the one allowed by codes of practice. For such structures, special analysis is needed to circumvent or prevent the formation of failure mechanisms that may be triggered during construction or when subjected to traffic loads. Therefore, special features, such as transverse stiffeners attached to the metal shell and the use of thrust concrete beams, may be required to assist the corrugated metal shell in carrying the loads. In this paper, a novel design is proposed for such structures in which the surrounding soil is reinforced and the metal shell is tied into the soil. A finite-element analysis of long span soil-metal structures with shallow soil cover is carried out using these two designs. The analysis is verified and substantiated using field data obtained during the construction of an 18 m soil-metal bridge. Comparing the structural response from the two designs shows that the latter design can lead to a superior structure.     

Free Vibrations of Cylindrical Storage Tanks: Finite-Element Analysis and Experiments

This note summarizes a theoretical and experimental study undertaken to provide a deeper understanding of the effect of different parameters on the coupled modal characteristics of circular cylindrical tanks. First, the most common case of clamped-free tanks resting on rigid foundations is investigated by using finite-element (FE) modeling and holographic experiments. A good agreement between experimental and numerical results is a basis to draw a number of conclusions. For both tank geometries investigated, the frequencies for modes of circumferential parameter n = 1 (the “beam” modes) are found to be reduced most significantly by the presence of liquid. Very significant dependence of the radial shell mode shapes on the filling ratio is confirmed both by the FE and experimental results. In addition, nonclassical vibration patterns for radial shell modes were extracted numerically and recorded experimentally. Special attention is paid to the pairs of shell modes. Second, the effects of a flexible foundation and axial compression are investigated using holographic interferometry. The modal responses of this shell–liquid system are found to be different from those of the existing theoretical models.     

Enhancement of Flexural Design of Horizontally Curved Prestressed Bridges

In this paper, flexural behavior of horizontally curved prestressed (posttensioned) box bridges is studied by using three-dimensional and refined finite-element modeling and analysis. Bridge length, section geometry, and material properties are the same in all the models, while angle of curvature varies from 0 to 90°. The results of analysis show that in curved bridges, stress distribution is significantly different in comparison to straight bridges. Also, the level of stresses at some locations of section width is considerably high. It is proposed to vary the distribution of the prestressing tendons across section width in order to optimize the bridge capacity. Results show that by proper redistribution of prestressing in section width, significant reduction in resultant stress is possible.     

Time-Dependent Reliability of PSC Box-Girder Bridge Considering Creep, Shrinkage, and Corrosion

Bridge performance undergoes time-varying changes when exposed to aggressive environments. While much work has been done on bridge reliability under corrosion, little is known about the effects of creep and shrinkage on the reliability of concrete bridges. In this paper, the CEB-FIP model for creep and shrinkage is applied by using finite-element (FE) analysis in conjunction with probabilistic considerations. Verification is made by comparing the analytical findings with existing test data. More specifically, a time-dependent reliability assessment is made for a composite prestressed concrete (PSC) box-girder bridge exposed to a chloride environment. This realized via an advanced probabilistic FE method. The postcracking behavior of the thin-walled box girder is described using composite degenerated shell elements, and importance sampling is used to improve the efficiency of the reliability analyses. It is shown that concrete creep and shrinkage dominate during the early stages of bridge structure deterioration. This is accompanied by a decrease in reliability owing to the combined action of creep, shrinkage, and corrosion. The reliability indexes for the serviceability and the tendon yielding limit state fall below the target levels prior to the expected service life. Therefore, early maintenance and/or repair measures are required.     

Analytical and Field Investigation of Roma Suspension Bridge

The Roma–Ciudad Miguel Aleman International Suspension Bridge is an historic unstiffened suspension bridge with a 192 m (630 ft) main suspended span, originally constructed in 1928. In 1997 the bridge was inspected and a full-scale nondestructive load test was conducted. The resulting experimental data are evaluated and compared to the results of analyses by finite-element method modeling. The history of the bridge is reviewed, with an emphasis on modifications and retrofits to the structure. The unique behavior and attributes of unstiffened suspension bridges are discussed in the specific context of this particular bridge.